Accept boolean as well as string (#119)

* Accept boolean as well as string

* Update math.html

Tidy it up

* Update CONTRIBUTORS.md

Add myself to contributors

CONTRIBUTORS.md

@@ -23,3 +23,4 @@
 - [Vlad Ionescu](https://github.com/Vlaaaaaaad)
 - [Joseph Ting](https://github.com/josephting)
 - [Abner Campanha](https://github.com/abnerpc)
+- [Martin Kiesel](https://github.com/Kyslik)

layouts/partials/posts/math.html

@@ -1,4 +1,4 @@
-{{- if eq .Params.math "true" -}}
+{{- if .Params.math -}}
   <script type="text/javascript" async
     src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-AMS-MML_HTMLorMML-full">
     MathJax.Hub.Config({